Generally, (meth)acrylic acid is prepared by gas-phase oxidation of propane, propylene, (meth)acrolein, etc. in the presence of a catalyst. For example, propane and propylene are converted to (meth)acrylic acid via (meth)acrolein by gas-phase oxidation in the presence of an appropriate catalyst in a reactor, and a reaction product gas mixture including (meth)acrylic acid, non-reacted propane or propylene, (meth)acrolein, inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid, low-boiling point by-products, high-boiling point by-products, etc.) is obtained in the back end of the reactor.
The (meth)acrylic acid-containing gas mixture contacts an absorption solvent containing water in a (meth)acrylic acid absorption tower, and obtained as a (meth)acrylic acid aqueous solution. Non-soluble gas from which (meth)acrylic acid is discharged is recycled to the synthetic reaction of (meth)acrylic acid, or a part thereof is converted to harmless gas by incineration, and discharged. The (meth)acrylic acid aqueous solution is obtained as (meth)acrylic acid by extraction, distillation, and purification.
Meanwhile, various methods have been suggested to improve recovery efficiency of (meth)acrylic acid by controlling process conditions or process order. A known representative method is a method for separating water and acetic acid from the (meth)acrylic acid aqueous solution obtained in the (meth)acrylic acid absorption tower by azeotropic distillation using a hydrophobic solvent in a distillation column.
In detail, by the azeotropic distillation method, water and acetic acid are recovered from the top portion of the distillation column and (meth)acrylic acid is recovered from the bottom portion of the distillation column. However, (meth)acrylic acid recovered from the bottom portion of the distillation column is recovered as a mixture with high-boiling point by-products, etc., and therefore, the liquid discharged from the bottom portion of the distillation column must be further distilled in order to remove high-boiling point by-products. A high-boiling point by-product separation process of removing high-boiling point by-products from the bottom discharge liquid requires a large amount of energy and also generates a problem that (meth)acrylic acid is exposed to high temperature during the process.